The First Mission to the Nearest Star
Solar Probe Plus will be a historic mission, flying into the Sun's atmosphere (or corona) for the first time. Coming closer to the Sun than any previous spacecraft, Solar Probe Plus will employ a combination of in situ measurements and imaging to achieve the mission's primary scientific goal: to understand how the Sun's corona is heated and how the solar wind is accelerated. Solar Probe Plus will revolutionize our knowledge of the origin and evolution of the solar wind.

On the final three orbits, Solar Probe Plus will fly to within 8.5 solar radii of the Sun's "surface" 8.5 solar radii is 8.5 times the radius of the Sun, or about 3.7 million miles. That is about seven times closer than the current record-holder for a close solar pass, the Helios spacecraft.
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